Duane syndrome is a disorder of eye movement. This condition prevents outward movement of the eye (toward the ear), and in some cases may also limit inward eye movement (toward the nose). As the eye moves inward, the eyelids partially close and the eyeball pulls back (retracts) into its socket. Usually only one eye is affected. Some people with Duane syndrome develop amblyopia ("lazy eye"), a condition that causes vision loss in the affected eye. Most cases occur without other signs and symptoms. There are three forms of Duane syndrome, designated types 1, 2, and 3. The types vary in which eye movements are most severely restricted (inward, outward, or both). All three types are characterized by retraction of the eyeball as the eye moves inward and are inherited in an autosomal dominant fashion.
Given the evidence that Duane syndrome (DS) results from an absence of the abducens nerve (cranial nerve VI) and aberrant innervation, and that it is associated with other anomalies in some cases, it is thought to result from a disturbance of normal embryonic development by either a genetic or an environmental factor at the time when the cranial nerves and ocular muscles are developing (between the third and sixth week of pregnancy). Genetic studies of two large families with DS inherited autosomal dominantly (without associated abnormalities) established that mutations in the CHN1 gene were found to be the cause in these and several other families.
Duane-radial ray syndrome (DRRS), inherited in an autosomal dominant manner, has been shown to be caused by mutations in the SALL4 gene. However, no SALL4 gene mutations were found in 25 sporadic cases of isolated DS (occurring in one individual in a family with no additional abnormalities).
DS can also be found as part of another complex autosomal recessive disorder (that can include deafness, facial weakness, vascular malformations and leaning difficulties) due to mutations in the HOXA1 gene. In addition, chromosome studies of individuals with DS and other abnormalities have, in rare cases, shown abnormalities that suggest other locations for genes responsible for causing DS.
Last updated: 3/21/2012
Is Duane syndrome inherited?
The majority of cases of Duane syndrome are sporadic (occurring in individuals with no history of the condition in the family). About 10% of affected individuals appear to have other affected family members. Both autosomal dominant (most commonly) and autosomal recessive forms of Duane syndrome have been documented. In some families with dominant Duane syndrome, it has appeared to "skip a generation" (showing reduced penetrance) and it has also been shown to range in severity within the same family (showing variable expressivity). Most familial cases are not associated with other anomalies. Given the large percentage of sporadic cases, it seems likely that both genetic and environmental factors play a role in the development of Duane syndrome amongst affected individuals.
Last updated: 3/21/2012
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